In existing apparatuses for handling fluids such as chemicals (chemical solutions), various fluid devices (for example, valves, regulators, various sensors such as pressure sensors, and various switches such as pressure switches) serving as constituent elements are connected with piping to provide an integrated fluid device unit structure (integrated structure). In such fluid device unit structures, a main fluid flow path for supplying a slurry-like chemical solution and a return flow path branched from the main fluid flow path are included, and each flow path is provided with a valve that is used for switching the flow path.
Furthermore, in cases where a plurality of chemical-solution fluid devices are used, for example, as in a semiconductor manufacturing apparatus, an integrated structure that enables coupling the chemical-solution fluid devices to one another without using piping is proposed. Since piping is unnecessary, it is expected that a reduction in the overall size of the apparatus is possible (for example, see Patent Citation 1).    Patent Citation 1: Japanese Unexamined Patent Application, Publication No. 2000-120903 (see FIG. 1)